This application claims the benefit of Japanese Patent Application Number 2012-038864 filed on Feb. 24, 2012, the entirety of which is incorporated by reference.
1. Technical Field
This invention relates to an oscillating rotary electric power tool in which a spindle with a distal end tool attached thereto is projected downward from a front end portion of a housing accommodating a motor so that the spindle will be driven by the motor to rotate clockwise and counterclockwise in an oscillating manner.
2. Background Art
As shown in FIG. 4, there is known a conventional oscillating rotary electric power tool 50, where a motor M is accommodated in a housing 51 extending in a longitudinal direction (horizontal direction of FIG. 4) of the oscillating rotary electric power tool 50, and a spindle 53 to which various kinds of distal end tools 52 are able to be attached is projected downward from a front end portion (right side in FIG. 4) of the housing 51 in an orthogonal direction with respect to the longitudinal axis of the housing 51. In this oscillating rotary electric power tool 50, a coupling member 55 is coupled in front of an output shaft 54 of the motor M in such a manner that a projected portion 58 of a crankshaft 57 is fitted in a depressed portion 56 provided on a front end face of this coupling member 55 to integrate the coupling member 55 and the crankshaft 57 in the rotational direction. Then, a link member 59 to which the spindle 53 is fixed is supported in front of the crankshaft 57 within the housing 51. As viewed from the front side of the oscillating rotary electric power tool 50, this link member 59 rotates clockwise and counterclockwise in an oscillating manner by the transmission of power from the crankshaft 57.
In the above oscillating rotary electric power tool 50, when the output shaft 54 of the motor M rotates, the link member 59 rotates clockwise and counterclockwise in a oscillating manner as a result of the transmission of the torque of the motor M to the link member 59 through the coupling member 55 and the crankshaft 57. Along with this, the spindle 53 fixed to the link member 59 and a distal end tool 52 rotate clockwise and counterclockwise in the oscillating manner. However, since the projected portion 58 is fitted in the depressed portion 56 with an allowance in the rotational direction, the depressed portion 56 and the projected portion 58 hit each other when the coupling member 55 and the crankshaft 57 rotate integrally along with the rotation of the output shaft 54, suffering from the disadvantage of generating abnormal noise in a hitting portion.
As a technique for preventing the generation of such abnormal noise, Japanese Utility Model Application Publication No. 49-111654 describes that projected portions and depressed portions are formed alternately in a circumferential direction on the end face of a cylindrical driving body and the end face of a cylindrical driven body facing each other, respectively. The projected portions of the driving body are fit into the depressed portions of the driven body and the projected portions of the driven body are fit into the depressed portions of the driving body, and an elastic body is inserted into a clearance gap between each projected portion and each depressed portion in the circumferential direction.